When unicasting, broadcasting, or multicasting is performed in a 4G LTE/LTE-A system and a 3G system of a mobile communication network, a receiver transmits a packet independent of appropriately receiving a transmitted signal mainly in an unacknowledged mode (UM). However, a broadcasting transmission scheme in the UM form has a limitation in communications for a special purpose such as a disaster network or communications having a mission critical character such as railway communication. Therefore, as an acknowledged mode (AM) form, there is a need to consider a form in which the receiver transmits whether to normally receive a packet to a transmitter in an ACK signal (acknowledgement response signal) or a NACK signal (non-acknowledgement response signal). However, in communication of such acknowledged mode (AM) form, there is a problem of increasing a retransmission frequency as the transmitter retransmits each of the packets which are not received by a receiver after the ACK signal or the NACK signal is received.
Recently, a technique of effectively transmitting packets to multiple receivers by using an index coding concept under the existing broadcasting/multicasting transmission environment has been proposed. Here, the index coding means that the transmitting side performs exclusive OR (XOR) operation processing on a plurality of packets. If the plurality of packets are index-coded to be transmitted as one packet, to select and receive packets which are not received by a receiving side, the packets which are not received correctly may be decoded by an exclusive OR operation of one packet which is subjected to the exclusive OR operation processing and the already received packet.
Further, unlike a STOP and WAIT method for transmitting one packet or receiving an ACK signal or a NACK signal, a go back-n method or a selective repeat ARQ method which is one of automatic repeat reQuest (ARQ) methods which are currently widely used at a retransmission technique of a mobile communication network is operated by a scheme of continuously transmitting packets within a specific window size, receiving an ACK signal or a NACK signal for all the transmitted packets and separately transmitting the packets which are not received correctly based on the received ACK signal or NACK signal, and sliding a window to perform a subsequent new transmission.
However, when the ARQ method is applied to the multicasting transmission environment, a terminal successfully receiving a specific packet redundantly receives packets previously received by retransmission, and as a result, radio resources may be inefficiently used, an unnecessary delay may occur, and a retransmission frequency may be increased.